Capacitor in a sealed metal case

ABSTRACT

An integral rigid axial electrical connector extends from an electrode of a capacitance section through an insulating plug closure in the open end of a metal casing. The connector provides a fluid tight seal with the insulating plug and serves as the mandrel on which the capacitance section is rolled.

I United States Patent [15] 3,662,236 Markarian et al. 1451 May 9, 1972[54] CAPACITOR IN A SEALED METAL [56] References Cited CASE UNITEDSTATES PATENTS [72] Inventors: Mark Markarian, Williamstown; Robert J.

3,015,759 H1962 Bugel ..3l7/200 X Adams Mass' 3,301,270 1/1 967 HOl'n..174/s2.s [73] Assignee: Sprague Electric Company, North Adams,

Mass Primary Examiner-E. A. Goldberg [221 F d M 12 197]Attorney-Connolly & Hut: and Vincent H. Sweeney 1e ar. 21 1 Appl. NO-Z123,722 [57] ABSTRACT An integral rigid axial electrical connectorextends from an electrode of a capacitance section through an insulatingplug 2? g 174/52 ka? closure in the open end of a metal casing-Theconnector pro. 1 f" 8 vides a fluid tight seal with the insulating plugand serves as the [58] Fleld 0 Search ..3 l7/242, 260, mandrel on whichthe capacitance section is rolled.

7 Claims, 4 Drawing Figures 13 i l 3o 25 26 1i 1 1: I I ll .5 1 .1 -fl'1 CAPACITOR IN A SEALED METAL CASE BACKGROUND OF THE INVENTION Thepresent invention relates to a capacitor contained in a metal casing andhaving a connection to one of its electrodes through the end closure ofthe casing, and more particularly to the provision of a rolled capacitorhaving a shock-resistant fluid-tight means for making the connectionthrough the end closure while facilitating the assembly of thecapacitor.

Rolled capacitors contain fluid materials which are impregnated into thecapacitor section to provide desired electrical properties. It isimportant to prevent the escape of such fluid in both liquid and gaseousstates from the capacitor during use. This use may include subjectingthe capacitor to rough physical treatment and particularly to vibrationand other physical shock. It is-important that the capacitor be capableof withstanding such extreme physical treatment without diminution ofthe vital'electrical characteristics or without involving a complicatedassembly.

One object of this invention is to provide a capacitor having improvedvibration resistance.

Another object of this invention is to provide an integral connection toone of the capacitor electrodes through the closure of the capacitorcontainer.

Another object of this invention is to provide an improved connectorconstruction which assists and simplifies the convolutely woundcapacitor assembly.

SUMMARY OF THE INVENTION A rolled capacitor in a metal casing has astraight rigid electrical connector made up of a mandrel and an enlargedrivetlike end extendingaxially through the insulated plug closing themetal casing. The capacitance section is rolled on the mandrel and therivet-like end is sealed within the insulating plug to provide aterminal surface on the outside of the terminalplug to which a lead wiremay be suitably attached. The rivet-like end is formed by welding theend of the mandrel to a flange insert in a central passage through theinsulating plug so as to form the tight seal between the axial connectorand the The combined connector and plug assembly may be in serted in therolling apparatus when the section is rolled on the mandrel.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an exploded view in elevationof an electrical connector provided in accordance with this invention;

FIG. 2 is an elevational view partially in section of the assembledelectrical connector of FIG. 1;

FIG. 3 is an elevational view of the electrical connector with acapacitor electrode attached; and

FIG. 4 is a view in section of an assembled capacitor in accordance withthe invention.

DETAILED DESCRIPTION OF THE INVENTION Convolutely wound capacitors arewell known in the art and comprise capacitance sections havingelectrodes separated by spacer material having dielectric properties. Itis also known to seal these sections in metal containers having one openend which is sealed closed by a stopper or plug positioned in theorificeof the container. The plug is in fluid tight engagement with thecontainer at the orifice. The electrodes are electrically connected byseparate conductors attached to the respective electrodes whichconductors extend from the capacitance section. One conductor isgenerally attached to the metal container and the other conductorgenerally extends to and through the closure plug.

The present invention involves a capacitance section in a casing whereinthe section has a straight rigid electrical connector from one of theelectrodes of the section secured in the closure plug of the casing. Theconnector comprises a stiff mandrel around which the convolutely woundsection is rolled and an enlarged river-like end which is fluid tightengagement with the plug closing the open end of the casing.

FIG. 1 shows the component parts of the straight rigid electricalconnector 10in an exploded view. A mandrel II has integrally formed atits upper end a flange 20 and a knob l2. A recessed plug 13 ispositioned between the knob 12 and a flanged insert 14. The plug 13 ispreferably composed of Teflon and is circumferentially recessed withagroove 15. A lead wire 16 is adjacent the insert 14. Theplug 13 has acentral passage 17. The mandrel 11 with knob 12 on its end. the passage17, and the insert 14 are depicted in FIG. I all aligned representingthe straight alignment of the component parts of the electricalconnector 10.

The knob 12 and insert 14 are joined to form a thick rivetlike end. 18of the connector 10 as shown in FIG. 2. The junction is obtained byinserting the ends of parts 12 and 14 into the passage 17 and buttwelding under current and pressure to unite them with their respectiveinsert flanges bearing against the flat radial surfaces of the plug 13.By this welding operation the knob 12 and insert 14 are formed into theend 18 with an enlarged joint 19 at the place of the junction in thepassage 17. This enlarged joint 19 is larger in diameter than thepassage 17 to exert great pressure on the walls thereof and form a veryfluid-tight engagement between the wall of passage 17 and the connectorend 18. The lead wire 16 is butt welded to the connector 10.

The operation of butt welding the knob I2 and insert 14 to form thejoint 18 within the plug 13 also serves to modify the contact betweenthe thick connector end 18 and the plug 13 so that the plug 13 adheresto the end 18. Similarly, the flanges 20 and 21 compressed against theradial surfaces of the plug 13 are firmly attached to the plug 13. Afluid tight seal is achieved between the axial connector 10 and the plug13.

The plug and connector assembly is completed as shown in FIG. 2 with aresilient annular ring 22 seated within the groove 15.

In order to produce the rolled body of the capacitor of this inventionthe mandrel portion 11 of the connector 10 is used as a winding mandrel.As shown in FIG. 3, the mandrel II is attached to the capacitorelectrode 24 by cold welding the electrode to the surface 23 of themandrel II and the electrode and the other electrode and the dielectricspacers are rolled as by placing the connector I0 in a chuck of asuitable rolling machine and wound into a compact section. In thepreferred embodiment, the anode electrode 24 is wound on the connector10 after the connector has been assembled within the insulating plug 13.

In FIG. 4 a completed capacitance section 25- is shown assembled in acasing 26 with the plug I3 closing the orifice at the open end of thecasing 26 by having the wall of thecasing 26 crimped into a concave beadindented into the ring 22 and the upper rim of the casing 26 rolled overto compress against the upper surface of the plug 13. Thus, the plug 13effectively seals the capacitor container against fluid loss.

At the inner end of the section 25 a tab 27 from the other electrode ofsection 25 is welded to the inside surface of the bottom of the casing26 and thus connects the other electrode, not shown, to the casing 26.The casing 26 is insulated from the connector 10 by the non-conductiveproperty of the plug 13. The capacitance section 25 is seated on aninsulating spacer 28 at the bottom of the inner end of the casing 26 tofurther improve the vibration resistance of the capacitor. A lead wire29 is welded to the outside surface of the casing 26 opposite the weldof tab 27.

The construction of the present invention can be used for othercapacitor types where an electrode connection is needed from within ametal container through an insulating plug. While in the describedpreferred embodiment the section is wound on the assembled connector andplug, the winding could be done before the connector is assembled withthe plug.

Among other advantages of this invention is the superior resistance tovibration including the ability to withstand 70G without failure. Thefeatures of the integral, rigid, axial connector are obtained withoutadding steps to the assembly procedure. A key feature is the rigidity ofthe integral connector along the capacitor axis. Also a fluid gas-tightseal between the connector and the plug is assured.

What is claimed is:

l. A capacitor having in combination a capacitance section made up of apair of conductive electrodes separated by dielectric material anddisposed in a metallic can sealed by a can closure, an integral stiffconnector having a mandrel member attached to one of the electrodeswithin the section and having an enlarged rivet end in the can closure,the connector extending axially through the can closure and soconstructed and arranged that the enlarged rivet end is pressed intotight engagement with the closure, and an end surface of the axialconnector extending out of the can.

2. A capacitor as claimed in claim 1 wherein the closure is aninsulating plug and the enlarged rivet end is in pressure engagementwith the plug.

3. A capacitor as claimed in claim 2 wherein radial flanges on theconnector bear against radial surfaces of the plug.

4. A capacitor as claimed in claim 1 wherein the mandrel member isprovided at one end with a knob, and the enlarged rivet end includes theknob butt welded to an insert in the can closure.

5. A capacitor as claimed in claim 1 wherein external lead wires areattached in axial alignment to the end surface and to the bottom of thecan, and a tab from the other of the pair of electrodes is attached tothe can.

6. A capacitor as claimed in claim 5 wherein the section is seated on aninsulating spacer at the bottom of the can, and the tab extends throughthe spacer into the attachment to the can.

7. A process for making a convolutely wound capacitor comprising thesteps of forming an electrical connector consisting of a mandrel havingat one end a knob, providing an insulating plug having a central passageand an insert with a radial flange and a shank proportioned to fit inthe passage, joining the knob and the shank in the passage to provide anenlarged rivet end within the passage, joining a capacitor electrodefoil to the mandrel, convolutely winding the attached foil with suitablespacers and another electrode to produce a capacitance unit, insertingthe capacitance unit in a metal container and attaching the otherelectrode to the inner surface of the container by a tab.

* i 1' I l

1. A capacitor having in combination a capacitance section made up of apair of conductive electrodes separated by dielectric material anddisposed in a metallic can sealed by a can closure, an integral stiffconnector having a mandrel member attached to one of the electrodeswithin the section and having an enlarged rivet end in the can closure,the connector extending axially through the can closure and soconstructed and arranged that the enlarged rivet end is pressed intotight engagement with the closure, and an end surface of the axialconnector extending out of the can.
 2. A capacitor as claimed in claim 1wherein the closure is an insulating plug and the enlarged rivet end isin pressure engagement with the plug.
 3. A capacitor as claimed in claim2 wherein radial flanges on the connector bear against radial surfacesof the plug.
 4. A capacitor as claimed in claim 1 wherein the mandrelmember is provided at one end with a knob, and the enlarged rivet endincludes the knob butt welded to an insert in the can closure.
 5. Acapacitor as claimed in claim 1 wherein external lead wires are attachedin axial alignment to the end surface and to the bottom of the can, anda tab from the other of the pair of electrodes is attached to the can.6. A capacitor as claimed in claim 5 wherein the section is seated on aninsulating spacer at the bottom of the can, and the tab extends throughthe spacer into the attachment to the can.
 7. A process for making aconvolutely wound capacitor comprising the steps of forming anelectrical connector consisting of a mandrel having at one end a knob,providing an insulating plug having a central passage and an insert witha radial flange and a shank proportioned to fit in the passage, joiningthe knob and the shank in the passage to provide an enlarged rivet endwithin the passage, joining a capacitor electrode foil to the mandrel,convolutely winding the attached foil with suitable spacers and anotherelectrode to produce a capacitance unit, inserting the capacitance unitin a metal container and attaching the other electrode to the innersurface of the container by a tab.